For years now, ultrasonic waves (i.e. high frequency acoustic waves) have been used to detect cracks, voids, porosity, and other internal discontinuities hidden in solid material such as metals, composites, plastics, and ceramics, as well as to measure thickness and analyze solid material properties. For instance, phased-array (PA) ultrasonic testing is an inspection technique which is known to be nondestructive, safe and, by now, well-established in the manufacturing, process, and service industries.
Phased-array ultrasonic testing involves the use of a search unit, typically including a conventional PA probe mounted on a conventional wedge, for propagating acoustic signals in a part to inspect and for detecting echoes of the acoustic signals within the part in order to localize and size flaws that may or may not exist in the inspected part.
During use, acoustic transducer elements of the conventional PA probe propagate the acoustic signals within the conventional wedge and through a wedge-probe interface before reaching the part to inspect. As the acoustic signals refract at the wedge-probe interface, some portion of the acoustic signals are generally reflected within the conventional wedge, toward a given larger end of the conventional wedge, which may cause noise if reflected back at any one of the acoustic transducer elements. In order to prevent these undesirable reflected acoustic signals from causing additional noise in the measurements, the conventional wedge generally has an acoustic damping structure at the given larger end for damping the undesirable reflections before they reach any one of the acoustic transducer elements. Although existing search units are satisfactory to a certain degree, there remains room for improvement.